Solar collector of fixed and concentrating flat panel type

ABSTRACT

Disclosed herein is a solar collector of a fixed and concentrating flat panel type in which V-band type absorption plates each configured to have coating layers formed on both surfaces thereof and configured to maintain regular intervals are formed within the solar collector having a flat panel type and a reflection plate configured to reflect solar energy toward the absorption plates and to have an elliptical symmetry structure are disposed under the absorption plates. Accordingly, a solar energy absorption ratio can be maximized, and concentration efficiency can be improved.

REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of Korean PatentApplication No. 10-2013-111492 filed on Sep. 17, 2013, the entirecontents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a fixed concentration type flat panelsolar collector and, more particularly, to a solar collector of a fixedand concentrating flat panel type, wherein the structures of thereflection plate and absorption plates of the solar collector areoptimized and a coating layer is formed on a surface of the absorptionplate, thereby being capable of improving concentration efficiency.

BACKGROUND OF THE INVENTION

As well known, a solar collector is basically divided into a vacuum tubetype solar collector and a flat panel type solar collector. Regardingthe vacuum tube type solar collector, China produces a solar energyconcentration area of 12 million m² or more per year based on the pricecompetitiveness of a bore-silicated glass tube, sells the solarcollectors in the domestic market, and also exports them to the Europeanmarket. In particular, Himin and Linuo in Shandong province, Qinghua inPeking, SunRain in Jiangsu province, and Vantage in QUangdong provinceare leading export companies, and they are threatening the solar energymarket of Korea after the second half of 2004.

A technical field using solar energy is gradually changed from a rangeof a relatively low temperature (about 60° C.) in the past to solarenergy cooling fields and industrial process heat use fields, and thus asolar energy use temperature is also expanded to about 60 to 150° C.Regarding the temperature range of the solar collector required in thesolar energy cooling field, a solar energy cooling system associatedwith an absorption type refrigerator requires about 95° C. In thedehumidification cooling field, water temperature of about 70° C. isrequired. There is a need to continue to develop new solar collectorssuitable for purposes.

In order for a solar collector to be used in such middle and hightemperature, the solar collector needs to have a very excellent thermalloss characteristic. A vacuum tube type solar collector and a CPC solarcollector belong to such a solar collector. However, such solarcollectors has many limits when a large amount of the solar collectorsare installed because the solar collectors are expensive and limited ininstallation.

In 2005, with the necessity of researches on a middle-temperature solarcollector, TASK 33/IV of IEA carried out researches on the development,performance improvement, and optimization of a middle-temperature solarcollector (having a range of 80 to 250° C.). Companies which productsuch middle-temperature solar collectors include Solaire, SCHUCO, AoSol,Solarfocus, PARASOL, and SOLITEM. Such a solar collector has beendeveloped to have a different structure and a concentrating type, thushaving good high temperature efficiency.

An energy concentration type solar collector using middle and hightemperatures may include a vacuum tube type, a Parabolic troughConcentrator (PTC), a Compound Parabolic Concentrator (CPC), a paraboliccomplex solar collector, and a parabolic dish depending on the geometricstructure of a concentrating form.

The use of such an energy concentration type solar collector isgradually increased in advanced countries due to the development ofprocess heat or solar energy cooling and solar energy in industrialsites because the energy density is very greater than that of anon-energy concentration type solar collector.

The CPC type solar collector is fixed without tracking the sun, and hasa solar energy absorption area smaller than a solar energy incident areaand is an energy concentration type solar collector capable of obtaininga range of a middle temperature (about 100 to 200° C.). The CPC typesolar collector may have an energy concentration cost of 10 or less, andmay obtain a desired temperature depending on selection.

A high-efficiency CPC solar collector basically includes a reflectionplate, an absorption plate, a heat transfer pipe, and a frame. Thehigh-efficiency CPC solar collector is chiefly developed and used inassociation with the vacuum tube type solar collector.

Such a CPC solar collector may be chiefly used in a solar energy coolingsystem for an industrial process that requires high-temperature energyof 70 to 150° C. and a solar energy cooling system that uses a hightemperature of about 95° C. because the solar collector may obtain ahigher temperature by concentrating energy through the concentration oflight.

Most of CPC solar collectors have relatively good performance becausethey have been developed in the form of a vacuum tube type solarcollector, but are expensive. Furthermore, the CPC solar collector hasmany disadvantages compared to a conventional flat panel type solarcollector because a high installation cost is required when installing alarge-scale commercial system because vacuum tubes must be assembled andthe design is complicated.

Recent researches on the CPC solar collector is chiefly focused on ascheme for increasing an energy concentration cost according to a changein the shape of a reflection mirror, the design of an absorber, and ascheme for improving performance through grafting with the vacuum tubetype solar collector. In such researches, localization researches havebeen partially carried out by some research institutes, and someproducts associated with the vacuum tube type solar collector have beendeveloped. However, the research and development and commercializationof solar collector products having a flat panel type solar collectorform are yet incomplete.

EXEMPLARY REFERENCES

Korean Patent No. 10-0692950 entitled “Flat-Plate Solar Collector usingChannel Type Absorber Plate (Mar. 3, 2007)

Korean Patent No. 10-0993809 entitled “Solar Collector Module andSystem” (Nov. 5, 2010)

Korean Patent Application Publication No. 20-2002-0047766 entitled “PlatType of Solar Absorber System Comprising Atransparent Insulator” (Jun.22, 2002)

Korean Patent No. 10-0388044 entitled “Panel of Solar Collector andApparatus for Manufacturing the Same (Jun. 4, 2003)

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and an object of the presentinvention is to provide a solar collector of a fixed and concentratingflat panel type, which is capable of maximizing a solar energyabsorption ratio by optimizing the structures of the reflection plateand absorption plates of the solar collector.

Another object of the present invention is to provide a solar collectorof a fixed and concentrating flat panel type, which is capable ofimproving concentration efficiency by forming a coating layer on asurface of an absorption plate.

In accordance with an aspect of the present invention, a solar collectorof a fixed and concentrating flat panel type configured to comprise ahollow frame 28, a cover 12, and a transmission body 20, and hollowabsorption pipes 22 and rises 24 for supplying an external thermalmedium and to have an insulator 14, a reflection plate 16, andabsorption plates 18 sequentially disposed within the solar collector,wherein the reflection plate 16 is configured to have an ellipticalsymmetry structure and to reflect solar energy toward the absorptionplates 18 as much as possible with respect to an incident angle of thesolar energy that varies according to each time zone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the configuration of a solar collectorof a fixed and concentrating flat panel type in accordance with anembodiment of the present invention;

FIG. 2 is an exploded view of the technical configuration of the solarcollector of a fixed and concentrating flat panel type illustrated inFIG. 1;

FIG. 3 is an enlarged view of the technical configuration of the solarcollector of a fixed and concentrating flat panel type illustrated inFIG. 1;

FIG. 4 is a cross-sectional view of an absorption plate 18 illustratedin FIG. 3; and

FIG. 5 is a graph illustrating a change of reflectance and a radiationfactor according to an NaOH ratio after the surface pre-processing ofthe absorption plate 18 in accordance with an embodiment of the presentinvention.

Description of reference numerals of principal elements in the drawings

10: solar collector 12: cover 14: insulator 16: reflection plate 18:absorption plate 20: transmission body 22: absorption pipe 24: rise 26:pipe connection body 28: frame 30a, 30b: coating layer

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention are described withreference to the accompanying drawings. In the following detaileddescription, some representative embodiments of the present inventionfor achieving the aforementioned objects are described below.Furthermore, other embodiments that may be proposed by the presentinvention are replaced with descriptions in the configuration of thepresent invention.

In an embodiment of the present invention, absorption plates of a V-bandform in which coating layers are formed on both sides within a solarcollector fabricated in a flat panel type are installed at regularintervals, and a reflection plate configured to reflect solar energytoward the absorption plates and to have an elliptical and symmetricalstructure are disposed under the absorption plates. Accordingly, a solarcollector of a fixed and concentrating flat panel type which is capableof maximizing a solar energy absorption ratio and improvingconcentration efficiency may be implemented.

FIGS. 1 to 3 are diagrams illustrating a solar collector of a fixed andconcentrating flat panel type in accordance with an embodiment of thepresent invention. The solar collector 10 in accordance with anembodiment of the present invention includes a hollow frame 28, a cover12, and a transmission body 20 that form a frame of a square form. Thesolar collector 10 includes an insulator 14, a reflection plate 16having an elliptical and symmetrical structure, and absorption plates 18of a V-band type which are sequentially installed within the solarcollector 10. The solar collector 10 further includes hollow absorptionpipes 22 and rises 24 for supplying an external thermal medium.

The reflection plate 16 and the absorption plates 18 correspond toessential elements of the present invention. The solar collector 10 isconfigured to increase an absorption ratio for solar energy and improveconcentration efficiency. This may be easily understood by the followingdetailed description.

Referring to FIGS. 1 to 3, the frame 28 that forms an outskirt squareframe of the solar collector 10 is chiefly fabricated by extrudingaluminum. In order to increase insulation performance, a hollow layer 28a is formed at the central part of the frame 28. Furthermore, a groovefor fixing the transmission body 20 on a front surface is formed in theframe 28. The transmission body 20 is shaped using transparent materialsor semi-transparent materials, and is made of glass materials.

The cover 12 is disposed in the rear of the frame 28, more specifically,at a point that faces the transmission body 20. The insulator 14, thereflection plate 16, and the absorption plates 18 are disposed betweenthe transmission body 20 and the cover 12. In this case, the hollowabsorption pipes 22 are disposed inside the frame 28 at both endsthereof, and a plurality of rises 24 is connected to the respectiveabsorption pipes 22. Connection pipes 26, that is, paths through whichan externally supplied thermal medium flows, are disposed at both endsof the absorption pipes 22 in the absorption pipes 22 and the rises 24.Such a configuration corresponds to a common technical configuration inconfiguring the solar collector 10, and a detailed description thereofis omitted.

The reflection plate 16, that is, one of the essential elements of thepresent invention, is disposed at the top of the insulator 14 as shownin FIG. 3. The reflection plate 16 is configured to increase anabsorption ratio for solar energy and to improve concentrationefficiency. That is, the reflection plate 16 is configured to have anelliptical symmetry structure in order to improve reflection efficiencyas much as possible. As shown in FIG. 3, the lower part of a shape, suchas an alphabetic letter “W”, rounded, and such shapes are connected toform the reflection plate 16. In such a configuration, the reflectionplate 16 may reflect solar energy toward the absorption plates 18 asmuch as possible with respect to an incident angle of the sun that isvaried depending on the time zone. Furthermore, reflection coatingprocessing has been performed on the front surface (i.e., a top surfacein FIG. 3) of the reflection plate 16 so that solar energy may bereflected.

As shown in FIGS. 3 and 4, the absorption plate 18 is configured in analphabetic letter “V” form. More specifically, the absorption plate 18is configured to have a V-band type structure and to absorb solar energy(or reflection light) reflected by the reflection plate 16 and directlyincident solar energy. As described above, the absorption plate 18 isconfigured to have the

V-band structure so that it is less changed as much as possible withrespect to modification in the length direction. Furthermore, the rises24 are arranged at the bottoms of the corners of the absorption plates18 in the middle of each of the absorption plates 18, as shown in FIG.4.

In particular, coating layers 30 a and 30 b are formed on the front andrear surfaces of the absorption plates 18 so that solar energy may beabsorbed as much as possible. The coating layers 30 a and 30 b may beselectively coated on both surfaces of or one surface of the absorptionplates 18. The coating layers 30 a and 30 b are formed using a coatingmethod and a composition to be described later.

The solar collector 10 configured as above according to an embodiment ofthe present invention has been implemented to have an optimum structurebased on a light absorption ratio according to each incident angle forsolar energy through computation analysis. The reflection plate 16 hasthe elliptical symmetry structure, and the absorption plate 18 has theV-band type structure. If the reflection plate 16 and the absorptionplates 18 were applied to the solar collector 10, solar energyabsorption ratios were 100%, 95.7%, 85.6%, 81.8%, and 89% at respectiveincident angles 0°, 15°, 30°, 45°, and 60°. It was revealed that a lightloss was small and the solar collector 10 had a sufficient function.Furthermore, an energy concentration cost was 2.4, that is, a relativelyhigh level. Accordingly, the solar collector 10 is a fixed energyconcentration type solar collector of a flat panel type through such anenergy concentration cost.

Table 1 below illustrates light absorption ratios according to incidentangles for solar energy through solar energy computation analysis.

In an embodiment of the present invention, the coating layers 30 a and30 b are formed on both surfaces of the absorption plates 18 as shown inFIG. 4. An absorption ratio for solar energy may be maximized becausethe coating layers 30 a and 30 b are formed. A light function wetsurface processing method for the absorption plates 18 is described indetail below.

Various types of oxidization layers, such as Cu2O and cupric oxide(CuO), may be formed on a surface of the absorption plate 18 made ofcopper (Cu) depending on thermal and chemical oxidization conditions.CuO, that is, black copper oxides, is a substance capable of functioningas a solar energy absorbent. In an embodiment of the present invention,the copper oxidization layer is made of potassium persulfate (KPS,K2S2O8), sodium hydroxide (NaOH), and sodium carbonate (SC, Na2CO3). Areaction generated in an oxidization solution is expressed in ChemicalEquation 1 below.

KPS/NaOH processing process

Cu+S₂O₈ ²⁻═CuSO₄+SO₄ ²⁻

CuSO₄+2NaOH═Cu(OH)₂(s)+Na₂SO₄(aq)

Cu(OH)₂(s)═CuO(s)+H₂O(I)  (1)

An SC processing process is a process of additionally processingunreacted CuSO4 into CuO in the KPS/NaOH processing process.

2CuSO₄+H₂O+2Na₂CO_(3═Cu) ₂(OH)₂CO₃+2Na₂SO₄+CO₂

Cu2(OH)₂CO₃═2CuO+CO₂+H₂O(I)

A process of determining a CuO structure is chiefly performed in theKPS/NaOH processing process. As may be seen from the above chemicalreaction mechanism, the structure and thickness of the oxidization layerare controlled by a ratio and processing time of KPS and NaOH. Ingeneral, the formed CuO oxidization layer has a needle and layer form ofa nano to micro size. As the thickness of the oxidization layerincreases, the oxidization layer gradually becomes dark and has a higherlight absorption ratio.

In such a case, an increase of the heat radiation factor inevitablyappears according to an increase of light absorption. Accordingly, theapplication of the oxidization layer to the absorption plates of a solarcollector is limited because most of absorbed solar heat is lost in aninfrared form. In an embodiment of the present invention, an oxidizationlayer having an excellent absorption ratio may be fabricated whilehaving the radiation factor as much as possible by optimizing thestructure and thickness of the oxidization layer. To this end, hydrogenperoxide may be used to form the structure of the oxidization layercapable of lowering reflectance and the radiation factor through surfacepre-processing. It was monitored that the CuO formation reaction withinthe KPS/NaOH solution was significantly delayed. Accordingly, optimumconditions were deduced by increasing the content and oxidization timeof NaOH. Compared to reflectance and the radiation factor of 15 and 15%in the initial product, excellent results in which reflectance and theradiation factor value were 10 and 10% were secured under the optimumconditions as absorption plates for solar energy after such surfaceprocessing. Meanwhile, FIG. 5 is a graph illustrating a change ofreflectance and the radiation factor according to NaOH ratios after thesurface pre-processing of the absorption plates 18.

In accordance with the present invention, the V-band type absorptionplates each having both sides coated are disposed within the flat paneltype solar collector, and the reflection plate configured to have theelliptical symmetry structure and to reflect solar energy toward theabsorption plates is disposed under the absorption plates. Accordingly,there are advantages in that solar energy that is incident at all anglescan be efficiently absorbed and the absorption ratio of the solarcollector can be maximized.

Furthermore, the present invention is advantageous in that theconcentration of solar energy is high compared to the 1:1 concentrationof a conventional solar collector through an energy concentration costof 2.4, a radiation loss area can be reduced through the front surfacesof the absorption plates, and a heat loss ratio of the solar collectorcan be significantly improved. Furthermore, the absorption plate of thepresent invention is advantageous in that it can improve concentrationefficiency because the coating layers are formed on both sides of theabsorption plate in order to properly absorb direct light and reflectionlight.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. A solar collector of a fixed and concentrating flat panel typeconfigured to comprise a hollow frame 28, a cover 12, and a transmissionbody 20, and hollow absorption pipes 22 and rises 24 for supplying anexternal thermal medium and to have an insulator 14, a reflection plate16, and absorption plates 18 sequentially disposed within the solarcollector, wherein: the reflection plate 16 is configured to have anelliptical symmetry structure and to reflect solar energy toward theabsorption plates 18 as much as possible with respect to an incidentangle of the solar energy that varies according to each time zone. 2.The solar collector of claim 1, wherein each of the absorption plates 18has a V-band type structure in order to maximize an absorption ratio. 3.The solar collector of claim 2, wherein coating layers 30 a and 30 bcapable of maximize the absorption ratio are formed on the absorptionplate
 18. 4. The solar collector of claim 3, wherein the coating layers30 a and 30 b are formed on both surfaces of the absorption plate
 18. 5.The solar collector of claim 3, wherein the coating layers 30 a and 30 bare made of potassium persulfate, sodium hydroxide, and sodiumcarbonate.
 6. The solar collector of claim 4, wherein the coating layers30 a and 30 b are made of potassium persulfate, sodium hydroxide, andsodium carbonate.